自工业革命后，全球气候变暖，对区域气候格局产生重大影响，为保障广东省水资源的科学配置、干旱灾情的合理应对以及生态环境的优化，本研究利用广东省76个气象站1971~2019年的长序列地面气象要素观测数据集，使用Penman-Monteith方法计算参考作物蒸散量，分析广东省近49年降水量（P）、参考作物蒸散量（ET₀）、湿润指数（HI）的时空变化趋势和主要气象要素（气温、相对湿度、风速、日照时数）对ET₀的敏感性和贡献率，探究广东省在过去49年干湿变化及其成因。主要结论如下：

（1）广东省总体较为湿润，HI在1.54~4.30之间；HI变化的倾向率为-0.09/10a，在过去49年间，广东省正经历由湿向干的变化趋势；在所有的研究站中：14.5%的研究站HI呈上升趋势，但上升站的趋势均不显著；85.5%的研究站HI呈下降趋势，而下降站中有32.8%的研究站为显著下降。

（2）HI反映区域的水分收入与支出，其收入项为降水量P，支出项为区域蒸散发量ET₀。在过去几十年间，区域上年平均P以-1.10mm/10a的速度下降：44.7%的研究站P呈上升趋势，但显著趋势的研究站仅占比1.3%（1个站）；55.3%的研究站P下降，变化趋势在统计上均不显著。同时，支出项ET₀在区域上以24.24mm/10a的速度上升：85.5%的研究站ET₀上升，且显著上升的研究站占比53.9%；ET₀下降的站仅占14.5%，显著下降的研究站占比1.3%。

（3）影响ET₀的4个主要气象要素近49年均呈现出显著的变化趋势：气温的所有研究站均呈现上升趋势，且97.4%的研究站显著上升，区域平均倾向率为0.25℃/10a；相对湿度、风速、日照时数总体呈现下降趋势，在区域尺度上：相对湿度以-0.73%/10a的速度下降；风速以-0.05(m/s)/10a的速度下降；日照时数以-0.06h/10a的速度下降。ET₀对气温、风速和日照时数为正敏感，对相对湿度为负敏感且敏感系数绝对值最大，表明ET₀与气温、风速和日照时数呈同方向变化，与相对湿度呈反方向变化且对相对湿度的变化最为敏感；变化量与敏感系数两者叠加得出贡献率：气温的所有研究站对ET₀均为正贡献，相对湿度对ET₀以正贡献为主，正贡献率的研究站占比86.8%，即气温和相对湿度总体上促进了ET₀的增加；风速和日照时数以负贡献为主，负贡献率的研究站占比分别为64.5%和69.7%，即风速和日照时数总体上导致了ET₀的减少；按其敏感系数绝对值平均数大小进行排序：相对湿度（16.66）>风速（10.35）>日照时数（1.66）>气温（1.01），ET₀受相对湿度的影响最大，受气温的影响最小。综上，相对湿度是导致广东省ET₀上升的最主要气候要素，同时也是影响广东省由湿向干变化的最主要气候要素，风速是导致广东省部分地区出现ET₀下降的最主要气候要素。

通过以上结果，可为全球变暖气候变化下解决广东省生态难题和推动广东省的可持续发展提供理论支撑，并可为后人研究广东省干湿变化和成因作为参考依据。

Since the industrial Revolution, global warming has had a significant impact on regional climate pattern. In order to ensure the rational allocation of water resources, response to drought and disaster and optimization of ecological environment in Guangdong Province, the long series data set of surface meteorological elements from 76 meteorological stations in Guangdong Province during 1971~2019 was used to calculate the Reference Crop Evapotranspiration by Penman-Monteith method in this study. By analyzing the spatio-temporal variation trend of precipitation(P), Evapotranspiration (ET₀) and Humid Index (HI) in Guangdong Province in the past 49 years, and the sensitivity and contribution rate of main meteorological elements (temperature, relative humidity, wind speed and sunshine duration), in order to explore the regularity and causes of Drought-wet Changes in Guangdong Province in the past 49 years. The main conclusions are as follows:

(1) Guangdong Province was generally humid, with HI between 1.54 and 4.30; In the past 49 years, Guangdong Province has experienced a trend from wet to dry, and the tendency rate of HI change is -0.09/10a. Among all the research stations, 14.5% showed an upward trend, but the upward trend was not significant. 85.5% of the sites showed a downward trend, and 32.8% of the declining sites showed a significant decline.

(2) HI reflects regional water income and expenditure, whose income item is precipitation P and expenditure item is regional evapotranspiration ET₀. In the past few decades, the average annual P over the region has decreased at a rate of -1.10mm/10a: 44.7% of the sites P showed an upward trend, but only 1.3% (1 site) showed a significant trend. 55.3% of the sites P decreased, and the change trend was not statistically significant. Meanwhile, the expenditure item ET₀ increases at a rate of 24.24mm/10a in the region: 85.5% of the sites ET₀ increased, and 53.9% of the sites increased significantly; Only 14.5% of the sites ET₀ experienced a decline, while 1.3% experienced a significant decline.

(3) The four main meteorological factors affecting ET₀ showed a significant change trend in recent 49 years: the temperature of all the research stations showed an increasing trend, and 97.4% of the stations increased significantly, and the regional average trend rate was 0.25℃/10a. The relative humidity, wind speed and sunshine duration showed a decreasing trend. At the regional scale, the relative humidity decreased at a rate of -0.73%/10a. The wind speed decreased at -0.05(m/s)/10a. Sunshine duration decreased at a rate of -0.06h/10a. ET₀ is positively sensitive to air temperature, wind speed and sunshine duration, and negatively sensitive to relative humidity, and the absolute value of sensitivity coefficient is the largest. It indicates that ET₀ changes in the same direction as air temperature, wind speed and sunshine duration, but in the opposite direction as relative humidity, and it is most sensitive to the change of relative humidity. The contribution rate was obtained by superposition of the change trend and the sensitivity coefficient: the temperature of all the research stations contributed positively to ET₀, and the relative humidity contributed mainly to ET₀, accounting for 86.8% of the stations, that is, the temperature and relative humidity promoted the increase of ET₀ on the whole. Wind speed and sunshine duration mainly contributed negatively to ET₀, with the percentage of negative contribution rates being 64.5% and 69.7%, respectively. In other words, wind speed and sunshine duration caused the decrease of ET₀ on the whole. The order of the absolute mean value of the sensitivity coefficients was as follows: relative humidity (16.66) > wind speed (10.35) > sunshine duration (1.66) > air temperature (1.01). ET₀ was most affected by relative humidity and least affected by air temperature. In conclusion, relative humidity is the most important climatic factor leading to the increase of ET₀ in Guangdong Province, and it is also the most important climatic factor affecting the change from wet to dry in Guangdong Province. Wind speed is the most important climatic factor leading to the decrease of ET₀ in some parts of Guangdong Province.

The above results can provide theoretical support for solving ecological problems and promoting sustainable development of Guangdong Province under global warming climate change, and can be used as reference for future generations to study the causes of Drought-wet Changes in Guangdong Province.